1. Field of the Invention
This invention relates to improvements in an airbag cover for covering at least a part of an airbag stored in its folded state, for example, inside a padded center of a steering wheel or an instrument panel.
2. Description of the Prior Art
Hitherto a variety of airbag restraint systems have been proposed and put into practical use. These systems are usually arranged as follows: When a deceleration at a vehicle collision is over a predetermined level, an initiator is ignited to start the operation of an inflator or gas generator, thereby inflating and developing an airbag folded state. Accordingly, a vehicle passenger is protected from coming into direct contact with an instrument panel and/or a front windshield. Such airbag restraint systems are usually provided separately for a driver seated on a driver's seat and for a vehicle passenger seated on a front seat beside the driver's seat. The airbag is stored in a padded center of a steering wheel for the driver while inside an instrument panel for the passenger beside the driver.
The thus stored airbag in its folded state is usually covered with an airbag cover to protect the airbag and keep the airbag in the folded state. The airbag cover is required to be readily and instantaneously broken to allow the air bag to smoothly inflate and project toward the driver or passenger through the broken airbag cover in a vehicle collision. In order to meet such a requirement, Japanese Utility Model Provisional Publication No. 63-155868 discloses an airbag cover which is generally box-shaped and formed of plastic. In this arrangement, a door-like structure is integrally formed at the front section of the cover, in which a fragile part is formed along the periphery of the door-like structure. A mesh member is embedded in the cover in a manner to avoid the fragile part, in which the mesh member at a position corresponding to the hinge of the door-like structure serves as a reinforcement member. With this arrangement, when the airbag inflates, the fragile part is broken and therefore the door-like structure turns around the hinge to open, thereby allowing the airbag to smoothly inflate to receive the face of the driver or passenger.
Another, another air bag cover as shown in FIGS. 5 and 6 of the drawings of the present application has been proposed, in which four nettings 3a, 3b, 3c, 3d disposed in a manner to cover an airbag 1', are embedded in foamed polyurethane. Each netting is generally L-shaped in section. In this airbag cover, a fragile part 5a is formed at the central portion of an upper section of the foamed polyurethane at which the ends of the nettings 3b, 3c are opposite to each other, maintaining a space therebetween, as shown in FIG. 6. With this arrangement, in a vehicle collision, high pressure gas is fed from an inflator to cause the airbag to inflate. Under the inflating force of the airbag, the airbag cover is broken along the fragile part 5a and the airbag develops toward a driver or a passenger, thereby receiving the face of the driver or the passenger.
However, drawbacks have been encountered in the above discussed airbag cover arrangements. In the case of the former conventional airbag cover disclosed in Japanese Utility Model Provisional Publication No. 63-155868, the mesh member is embedded in the plastic body, and therefore the structure of the airbag cover is unavoidably complicated, increasing the steps of the production process, and thereby raising the production cost.
In case of the latter airbag shown in FIGS. 5 and 6, the four nettings are covered with the foamed polyurethane in a manner to be embedded, and therefore a complicated plastic molding process is necessary while requiring a skilled worker during production of the airbag cover. This also increases the production cost of the airbag cover.